This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Persistent diarrhea is one of the leading causes of morbidity in captive nonhuman primates (NHPs). During the current reporting period, a cross-sectional study was continued to test fecal specimens obtained from rhesus macaques admitted to the veterinary clinics for diarrhea and/or wounding as well as from animals housed in field cages at the Tulane National Primate Research Center (TNPRC) for microsporidia shedding using PCR diagnostics. Of 194 clinic specimens analyzed, 28 of 95 (29.5%) were positive for microsporidia and of 99 field specimens analyzed, 35 of 99 (35.4%) were positive for microsporidia with an overall prevalence of 32.5%. Fisher's Exact test indicated no significant differences in prevalence associated with gender, age, or clinic vs field animals. Enterocytozoon bieneusi was by far, the most common species identified (54 of 64;84.3 %). The objective of this study is also to determine the prevalence of anti-norovirus (NoV), sapovirus (SaV) and Tulane calicivirus (TV) antibodies in rhesus macaques of the TNPRC and evaluate the antigenic relationship between these viruses. So far, we tested 515 rhesus macaques for this purpose. A high prevalence of NoV (51-61%) and SaV (50-56%) binding antibodies and TV (69%) neutralizing antibodies were detected. The high prevalence of human and rhesus CV-specific serum antibodies suggests the frequent exposure of colony macaques to enteric CVs including the possibility of CV transmission between human and NHP hosts. More recently, 325 randomly selected stool samples collected from TNPRC rhesus macaques were tested using modified degenerate primers targeting conserved amino acid motifs in the calicivirus RNA dependent RNA polymerases (RdRp). Thirty-six (11%) of the 325 stools samples tested yielded TV specific sequences, confirming that TVs are endemic in the TNPRC. According to phylogenetic analysis, the 36 TV isolates can be classified into two genogroups and at least four genetic types.